Dental articulators



Sept. 18, 1956 cs. A. BERGSTROM DENTAL ARTICULATORS 2 Sheets-Sheet 1 Filed Nov. 10 1951 Sept. 18, 1956 G. A. BERGsTROM 2,763,061

DENTAL ARTICULATORS Filed Nov. 10 1951 2 Sheets-Sheet 2 A UM? United States Patent DENTAL ARTICULATORS Gunnar A. Bergstriim, Orebro, Sweden Application November 10, 1951, Serial No. 255,763

Claims priority, application Sweden November 10, 1950 Claims. (Cl. 32-32) This invention relates to dental articulators and more particularly to the joints by which the lower and upper model-holding members of such articulators are hinged to each other.

For a better understanding of the invention reference may first be made to some details of the masticating mechanism by human beings. The condyles positioned one at the end of each backwardly projecting leg of the mandible articulate in sockets formed on the skull at the rear ends of the cheek-bones. The joints are so formed as to permit the condyles of slight movements more or less in practically all directions within the sockets so that the mandible becomes capable not only of a rotary movement about the axis through the two condyles, the condyle axis, but also of translatory movements longitudinally forwards and to some extent backwards from the normal or centric position and also laterally which movements make feasible the grinding effect of the chewing operation. In its longitudinal movement each condyle follows a surface in the joint forming the condyle path. The path slopes more or less downwards in a direction towards the incisors and the sloping is practically rectilinear within the range of movement normally employed in mastication. The inclination increases as a rule in the most protrusive as well as in the most retrusive positions.

In an articulator, models of the upper and lower jaws shall be subjected to movements imitating the natural mastication and, therefore, the models are mounted in upper and lower model-holding members hinged to each other by joints, the positions of which relative to the models approximate those of the condyles relative to the natural jaws. In the type of articulators to which this invention pertains each joint consists of a pivoting rod or pin secured to one of the members and a condyle disc secured to the other member, said disc having a slot shaped at least approximately to correspond to the condyle path. Usually the one end of the slot corresponds to the centric or normal position of the jaws, in which the incisors of the lower jaw, as a rule, stand inside those of the upper jaw. This end of the slot is preferably positioned at the centre of the disc. In operating the articulator the pivoting pins are placed at said centres of the discs and the models are secured to the holders to match each other as in the centric or normal position of the jaws. In order to imitate as far as possible the masticating movement of an individual patient the condyle discs are made rotatable in sockets provided in the model-holding member so as to be adjusted according to the condyle paths of the patient. For the purpose of determining the inclination of the slot of the disc the models shall be set in a protrusive position, that is with the incisors of the lower jaw about 5 millimeters forwardly of the centric position, and for warranting a correct position an impression pattern, a check-bite, in a plastic material, such as wax or plaster, is taken from the mouth of the patient, the jaws in the protrusive position. The check-bite is then placed to match with its. one side the one model and the operator with his one hand manipulates the holding'r'nembe'r carrying the other 2 model to cause that model to match the other side of the check-bite and, at the same time, he turns the discs so that the pivoting pins on the other holding member slide in the slots to positions suiting the appropriate protrusive position. By this manipulation it is very difficult to avoid damaging the check-bite and, therefore, the adjustment of the condyle discs may easily become incorrect. Furthermore, this adjustment is rather inconvenient.

lt is the object of this invention to provide an articulator having joints permitting a correct adjustment of the condyle discs. Another object is to make such adjustment feasible without damaging plastic check-bites. A further object is to make possible an adjustment in a rapid and convenient manner.

The invention will now be described with reference to some embodiments illustrated in the attached drawings, but it is to be understood that the invention is not confined to the structures thus described but shall be taken in its broadest aspects.

In the drawings:

Fig. l is a perspective view of a dental articulator of the type in which the present joint may with advantage be employed.

Figs. 2 and 4 to 15 are side views of various modifications of joints embodying the present invention, and Fig. 3 is a front view of the joint of Fig. 2. Figs. 2 to 5 show a structure comprising a sliclable and swingable control plate in different positions; Figs. 6 to 8 show a structure comprising a control plate slidable in a rotatable sleeve; Figs. 9 and 10 show embodiments in which the control member is a slidable rod; Figs. 11 and 12 show an embodiment comprising a sleeve rotatably mounted on a cylinder; Fig. 13 shows an embodiment having a swingable arm for forming the condyle slot, and Figs. 14 and 15 show an embodiment having a curved condyle slot.

In the articulator illustrated the lower model-holding member consists of a horizontal base 1 having two stands 2 and three feet 3 one below each stand and the third at the front. At a central point of the base is a support disc 5 to which a holder plate (not shown) for the lower jaw model is to be secured by means of the screw 4. A pivoting pin 9 projects inwardly from the top of each stand 2. The positions of the stands and the pins 9 relative to the position of the lower model are calculated to correspond approximately to the position of the condyle axis relative to the lower jaw of a human. The upper modelholding member consists of a bracket 10 secured to a bar 11, which is horizontally positioned between stands 2 substantially coaxially with pins 9. The ends of the bar are cylindrical and to these cylindrical ends the two condyle discs 12 are rotatably secured in a manner to be fixed thereto by means of screws 13. Various embodiments of the condyle disc will be described more in detail hereinbelow. Vertically above the lower support disc 5 the bracket 10 has similar support disc 16 to which the holder plate 17 for the upper jaw model is attached by means of the screw 4. A vertical rod 20 is provided at the front of bracket 10 for preventing the bracket from swinging down, and the position of the bracket can be adjusted by setting the rod in a suitable vertical position by means of setting screw 21.

In a preferred embodiment the condyle disc consists of a cylinder 30, one axial opening of which is partly covered by a guide member in the form of the stationary disc plate 31 secured to the cylinder by the cover plate 32 screwed to the cylinder by screws 33. At the portion of the cylinder opening not covered by plate 31 an interspace is formed between the end surface of the cylinder and the cover plate 32. The plate 32 has a window 34 shown at the lower right hand quadrant thereof. Plate 31 has a shoulder 35 at the centre against which the pin 9 can hear. The shoulder is formed by the plate 31 being recessed to form a lower sliding edge 36 and an upper guiding edge 37 corresponding to the condyle path. This guiding edge is straight but may be curved as the edge 37 of the disc illustrated in Figs. 14 and 15, so as to correspond more accurately to the true condyle path, particularly in case more protrusive points shall be determined. A control member in the form of a movable control plate 40 is provided to cooperate with plate 31 and, like 31, is recessed. Plate 40 has a shoulder 41 and is slidable in the interspace between the end surface of the cylinder 30 and the cover plate 32. In the position illustrated in Fig. 2, it bears against the edges 36 and 37 of plate 31 by complementary edges and against pin 9 by its shoulder 41. The plate is secured in this position by a small ball 42 housed in a boring in the cylinder and pressed by a spring partly into a hole 43 (see Fig. 4) in the plate 40. This is not particularly illustrated since it is a conventional means for loosely securing sliding parts to one another.

Fig. 4 illustrates the protrusive position. Plate 40 is loosened from ball 42 and is hanging by hook 47 on a small pin 48 projecting from the cylinder 30 into the interspace below the cover plate 32, thereby enlarging the opening below edge 37 to form an adjustment opening 51. In Fig. 5 the cylinder has been slightly rotated about its support on bar 11 so as to contact pin 9 and the control plate 46 is again brought into engagement with the guide plate 31 and is secured in this position by the ball 42 partly entering hole 44. The plates 31 and now form a condyle slot 49.

In the operation of this embodiment the condyle disc l2 is first set by screw 13 in the position illustrated in Fig. 2, the pin 9 being in the centre of the disc. The jaw models made for a patient, built up on their model plates, are attached to the discs 5 and 16 in accurate centric position relative to one another. This position corresponds to the centric relation of the natural jaws. The control plate 40 is now loosened as in Fig. 4 and a protrusive cheek-bite obtained from the patient is placed in position on the lower jaw model and the upper model can now easily be placed directly in correct position without deforming the check-bite, because the pivoting pins 9 have ample space for moving freely in the big adjustment opening 51. The longitudinal movement is usually of the order of 4 to 6 millimeters and the individual variations of the sloping of the condyle path are considered to stay within It being assumed that in the protrusive position of the models the relative position of the pin 9 and control plate 31 is that shown in Fig. 4, the operator releases the condyle disc unit 12 by screw 13 and rotates one disc at a time until the edge 37 of plate 31 contacts pin 9 which is easily felt but may also be seen or heard or ascertained in some other suitable way as by connecting pin 9 and plate 31 to an electric circuit containing a signal lamp. Being in contact position the discs are set by screw 13 and the control plate 48 is set in the position illustrated in Fig. 5. After removal of the check-bite the artificial articulation can now take place in the usual way, it being understood that the forces exerted, as by grinding, on the upper model are directed downwards so that the plate 40 will hardly be subjected to any strain and the locking by ball 42 will be satisfactory.

In Figs. 6, 7 and 8 an alternative performance of the disc unit is illustrated. In this case the disc cylinder 30' has a sector-shaped guide plate 31', and the control plate 40 is slidably mounted in a holder 53 rotatably sleeved on the end of the cylinder. The only important part of the plate 31 is the condyle path edge 37' ending near the protruding stop edge 54 of the rotatable holder 53. The control plate 49 has a shoulder 41' to embrace pin 9 and engages in Fig. 6 the plate 31' so that when these parts are locked, as by a ball and hole lock as illustrated in Figs. 25 by reference numerals 42 and 43, 44, respectively in this position the pin 9 is enclosed in the central position. Upon turning sleeve 53 through about 90 relative to the cylinder and extracting plate 40' the full open position illustrated in Fig. 7 is attained. After turning the cylinder and thus the entire disc unit until contact is obtained between edge 37' and pin 9, turning sleeve 53 back until plate 40' contacts edge 37 and locking plate 40' in its outer position, the articulating position illustrated in Fig. 8 is obtained. The operation of this modification will be obvious in view of the description referring to Figs. 2. to 5.

Fig. 9 illustrates still another modification. The central boring of disc cylinder 30" is partly obstructed by the guide plate 31" which leaves somewhat more than a quadrant open. The guide edge 37" of the plate is displaced by half the diameter of pin 9 from the geometric centre of the boring and at the same distance below the centre a control rod 60 is longitudinally slidable in a path parallel to said edge. The rod can be set in any one of three main positions by means of a spring 61 adapted to enter transverse grooves 62, 63, 64 on the rod 60. In the most inserted position of the rod the spring 61 engages groove 62 and the rod forms in cooperation with edge 37 the slot 49 in which the pin 9 moves during the articulation. A nose is placed at the end of the rod, on the side opposite to-the grooves. It is so positioned relative to groove 63 that when the rod is fixed in the position where spring 61 engages this groove 63, it bears against the pin 9 so as to fix the latter in the centre. The rod 60 can be turned so that when pulled further outwards the nose 65 passes below the pin. When pulled to the position in which the spring 61 engages the innermost groove 64 the adjustment opening 51 is free.

If it should be desired to fix the pin 9 in other positions than the central one, a modified type of the device of Fig. 9 may be used. This modification is illustrated in Fig. 10. Further to the elements shown in Fig. 9 this device has an additional nose 66 at a distance from nose 65 permitting the pin 9 to be fixed between the two noses and the guiding edge 37". The rod may be set in any convenient position by the set screw 67.

Still another embodiment is shown in Figs. 11 and 12. In this case,a sleeve'68 is journaled on the cylinder. The cylinder has an end plate 70 provided with the usual adjustment opening 51 for-the pivoting pin. The sleeve has also an end plate 71 provided with a similar opening 72. As illustrated in Fig.11, opening 72 is set 180 apart from opening 51 and in this position the openings overlap inthe centre only so as to form a common opening in which the pivoting pin 9 fits. This corresponds to the centric position of the jaws or models. Upon turning the sleeve through 180 opening 72 will register with opening 51 constituting the free space position in which the models can be set in the protrusive position, at which-the pin is situated in a position displaced from the centre. The cylinder being swung so that guide edge 37" contacts the pin 9, the sleeve can be turned through to the position shown in Fig. 12 in which the edge 73 at the opening 72 is parallel to edge 37", thereby forming the condyle slot 49.

Fig. 13 shows a modified condyle disc having a quadrant-shaped opening 51 positioned relative to the pivoting .pin as described with reference to the above embodiments. .An arm 77 is swingably mounted in a recess 78 in the disc about. a shaft 79 passed through a boring in the disc. The condyle slot 49 is formed by the guide edge 37" in cooperation with arm 77 when the latter is in the position shown. No means is here provided for locking the pivoting pin in the central position. Such means may be dispensed with. .When the arm is swung out from theposition illustrated the adjustment opening 51 is formed.

In the embodiments so far described the guiding edge has been shown as rectilinear. Figs. 14and l5 illustrate a structure having a condyle slot and a guide edge 37 curved to better correspond to the true condyle path.

, The rotatable disc plate 31" has an adjustment opening positioned'substantially within one quadrantpof the circular field about the rotary centre of the disc. The guide edge 37 of the plate is inclined at both ends. The control plate 80 is secured to a rod 81 passed through a boring in plate 31 and having a knob 82 by which the control plate can be rotated and also, when turned through an angle of 90, be pulled into a slot 83 in the plate 31". The control plate 80 has a recess 84 in the one edge at the centre of the plate 31 accommodated fixedly to hold pin 9 when in the centric position, as seen in Fig. 14. When turned through 90 and pulled into the slot 83 the withdrawn plate leaves the adjustment opening 51 free. The disc plate 31 having been rotated to contact the displaced pin 9 the control plate 80 is pushed into the opening 51 again and turned a further quarter of a revolution so that the edge 85 opposite to recess 84 will face the guide edge 37. The edge 85 has a configuration parallelling that of edge 37 so that a condyle slot 49 is formed between said edges as illustrated in Fig. 15.

What I claim is:

1. A dental articulator having upper and lower modelholding members, two pivoting pins secured to one of said members in substantially coaxial relationship to one another, two condyle discs secured to the other of said members rotatably about axes coaxial with said pins, each disc being adapted in one disposition of its members to present a radial slot of a width substantially equal to the thickness of said pin and extending from the centre of the disc outwardly for a length substantially equal to the normal condyle path of the lower jaw of human beings, said discs being positioned to receive in said slots one each of said pins so as to be pivoted thereon, at least one of said discs comprising a guide member stationarily secured thereto and a control member movably fitted therein, said guide member being provided with a condyle path-forming edge extending substantially radially of the disc, an axial adjustment opening in the disc confined at one side by said condyle path-forming edge and extending at least 5 millimeters from the centre of the disc for at least about 50 degrees from said edge, said control member being provided with a controlling edge and being movable relative to said guide member so that in one position said controlling edge will form in cooperation with said condyle path-forming edge said slot and in another position to leave said adjustment opening free and locking means in connection with said control member adapted to lock releasably said control member relative to said guide member at least in the first of said positions.

2. A dental articulator having upper and lower modelholding members, two pivoting pins secured to the lower of said members in substantially coaxial relationship to one another, two condyle discs secured to the other of said members rotatably about axes coaxial with said pins, each disc being adapted in one disposition of its members to present a radial slot of a width substantially equal to the thickness of said pin and extending from the centre of the disc outwardly for a length substantially equal to the normal condyle path of the lower jaw of human beings, said discs being positioned to receive in said slots one each of said pins so as to be pivoted thereon, at least one of said discs comprising a guide member stationarily secured thereto and a control member movably fitted therein, said guide member being provided with a condyle path-forming edge extending substantially radially of the disc, an axial adjustment opening in the disc confined at one side by said condyle path-forming edge and extending at least 5 millimeters from the centre of the disc for at least about 50 degrees from said edge, said control member being provided with a controlling edge and being movable relative to said guide member so as in one position said controlling edge will form in cooperation with said condyle path-forming edge said slot and in another position to leave said adjustment opening free and locking means in connection with said control member adapted to lock releasably said control member relative to said guide member at least in the first of said positions.

3. A dental articulator of the type described for hinging upper and lower model-holding members to each other, comprising a pivoting pin secured to one of said members and a disc unit rotatably secured to the other of said members, said disc unit containing a rotatable cylinder, a central axial opening in said cylinder, a guide plate secured to said cylinder transversally over said opening, said guide plate having a guide edge arranged to permit said pivoting pin to move along said edge from the center of said cylinder radially outwards, a control member having a control edge paralleling said guide edge, said control member being movable relative to said guide plate and adapted in one position to be fixed with said control edge parallel to said guide edge to form a slot and in another position to be removed to leave said axial opening free.

4. A dental articulator as claimed in claim 3, comprising a cover secured to said cylinder over said guide plate to form a slit between the end surface of the cylinder and the cover, said control member being in the form of a control plate, said control plate being arranged slidable in said slit.

5. A dental articulator as claimed in claim 4, in which said control plate has a projection, a hook being formed in said projection, a pin in said slit arranged longitudinally of the cylinder, said hook and said pin being arranged so that the hook can in one position of the control plate embrace said pin and be swung about said pin.

6. A dental articulator as claimed in claim 3, comprising a sleeve rotatable about said cylinder, an end plate secured to the one end of said sleeve, said end plate forming a slit in cooperation with the end surface of said cylinder, said control member being in the form of a control plate, said control plate being arranged to slide in said slit.

7. A dental articulator as claimed in claim 3, comprising a control rod, a boring in said cylinder adapted to fit said control rod so that the latter can be moved longitudinally in the boring parallel to said guide edge so as in an inserted position to form a slot in cooperation with said guide edge and in an extracted position to be removed from cooperation with said guide edge.

8. A dental articulator as claimed in claim 7, comprising a control rod rotatable in said boring, at least one nose on said control rod near the inner end thereof and adapted to hold intermittently said pivoting pin.

9. A dental articulator as claimed in claim 3, comprising a sleeve rotatably mounted on said cylinder, a control plate secured to said sleeve, a substantially quadrantshaped opening in each of said guide plate and control plate, said openings registering with each other in one relative angular position of said sleeve to said cylinder and having such extension as in a position set through 180 from said position of registering to form a central opening having substantially the same diameter as said pivoting pin and in one position set from said position of registering to form a radial condyle slot.

10. A dental articulator as claimed in claim 8 having two noses on said control rod near the inner end thereof, the distance between said noses being adapted to permit said pivoting pin to be fixed between the noses and said guide edge, and having an arresting member arranged to fix said control rod in a position between said inserted and said extracted positions.

References Cited in the file of this patent UNITED STATES PATENTS 1,906,797 Lentz May 2, 1933 2,428,808 Miller Oct. 14, 1947 FOREIGN PATENTS 358,811 Germany Sept. 16, 1922 586,011 Germany Oct. 26, 1933 

